This application claims the priority of Provisional Application Ser. No. 60/326,205, filed Oct. 2, 2001, the disclosure of which is expressly incorporated by reference herein.
The ability to interconnect computers and other intelligent devices is a common requirement wherever people live and work today. The electrical connection required to form this local area network (LAN) has traditionally been accomplished by installing dedicated data wiring both inside buildings and between clusters of buildings. A number of wireless (i.e. radio) methods have also been developed and deployed to address this need.
More recently, technology to allow electric power wiring infrastructure to simultaneously transport data at high rates has been realized. This Power Line Carrier (PLC) technology typically uses modulated radio frequency (RF) signals below 50 MHz conducted on the power wiring to transport the data.
There are significant practical advantages offered by PLC technology—namely that electrical wiring, of necessity, must be installed and that data connectivity can therefore be immediately added at little (or no) additional cost, particularly in existing buildings. Similarly, electrical outlets are ubiquitous within modern buildings and significant operating convenience is realized when data is simultaneously available at every outlet.
Another advantage of PLC technology is that the range that can be achieved is significantly greater than wireless methods, particularly in commercial buildings constructed of heavier materials that severely attenuate wireless signals. Yet another advantage of PLC technology over wireless methods is that the data is inherently more secure since a physical connection is required to join the network.
The invention described here addresses several important problems that arise in the installation and use of PLC technology for local area data networks.
Most contemporary LANs are configured in a “hub and spoke” topology where a central server device supports a number of users and also provides a gateway to the Wide Area Network (WAN) and/or the Internet. Maximum utility for a PLC network is obtained when its' physical configuration mirrors the logical topology of the LAN, i.e. when the PLC gateway is effectively located at the “electrical center” of the space such that every outlet is served with the best possible PLC signal. This point is often a rarely accessed electrical panel in a service closet or the basement and is almost never co-located with other data processing equipment. The invention provides a simple means to remotely inject the PLC signals at this optimal point.
Another important issue, particularly in commercial buildings, is that 3-phase electrical power/wiring is commonly used and adequate coverage of a PLC network within the building is achieved only when all three phases are excited with the PLC signal. The invention provides for the simultaneous excitation of all 3 phases of power wiring with a single PLC signal.
Yet another related issue arises during the installation of PLC networks in environments that have natural barriers to the signals (or block them entirely). A common situation is where a building has been modified and all sections no longer share a common source of electrical power. Another common situation is where power is supplied from a central point and then distributed to sections of the space via transformers, often for purposes of distribution efficiency or electrical isolation. The invention also provides a simple and flexible means to inject a single PLC signal into any number of remote points as required to obtain adequate coverage.
The system according to the present invention interfaces a communicating signal with a three-phase power network of a building by feeding a power line carrier signal to a remotely located coupling device which is constructed to enable each of the three phases to be supplied with the PLC signal from the remote signal source. In another respect of the present invention, the signal can be fed to two or more different parts of a building having different electrical isolation qualities with respect to PLC signal by providing separate coupling device for each part of the building.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.